Picture and map projector



T. C. FURNAS, JR

PICTURE AND MAP IBROJECTOR Nov. 25, 1947.

Filed May 4, 1945 4 Sheets-Sheet 1 NOV 25, 1947 T. c. FURNAs, JR

PICTURE AND' MAP PROJECTOR Filed May 4, 1945 4 Sheets-Sheet 2 AMM TM C.

Nov. 25; 1947. 4 f, FURNAS, JR 2,431,612

' PICTURE AND MAP PROJECTOR Fi1ed May 4, 1945 4 sheets-sheet 3 FIGB.

Nov. 25, 1947. zT C, FURNAg, JR 2,431,612

PICTURE AND MAP PROJECTOR Filed May 4, 1945 4 Sheets-sheet 4 m n l /V N Patented Nov. 25, 1947 UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to projectors, and with regard to certain more specic features, to projectors for reproducing maps, pictures and similar data, preferably by tracing.

Among the several objects of the invention may be noted the provision of an adjustable projector in the form of a convenient tracing table on which is provided a convenient horizontal working surface for tracing either enlarged or reduced projected data without shadow interference; the provision of apparatus of this class in which all optical projection parts are protectively housed; the provision of apparatus of this class having illuminating means such that markings on one side of a sheet may be projected without interference from markings on the other side at a reduced or enlarged scale; the provision of a projector of the class described having convenient visible means for indicating degrees of enlargement or reduction and which has accessible controls for changing said degrees; and the provision of apparatus of this class which is economical to construct. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings in which are illustrated several of various possible embodiments of the invention,

Fig. 1 is a longitudinal section of one form of the invention;

Fig. 2 is a plan View taken on line 2-2 of Fig. l;

Fig. 3 is a vertical section taken on line 3-3 of Fig. 1;

Fig. 4 is a vertical section taken on line 4-4 of Fig. 1;

Fig. 5 is a vertical section taken on line 5-5 of Fig. 1;

Fig. 6 is a vertical section taken on line 6-6 o-f Fig. 1;

Fig. '7 is a developed view on a reduced scale showing a completely extended light-control curtain;

Fig. 8 is a side elevation on a reduced scale, partly in section, showing an alternative embodiment;

Fig. 9 is a view similar to Fig. 1. showing another embodiment. parts being broken out in order to reduce the height of the figure; and,

Fig. 10 is a plan view of the lower broken-out parts of Fig. 9.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Heretofore projection apparatus for providing an image to be traced or otherwise duplicated has more or less followed the conventional lines used for ordinary photographic projection, the convenience of a tracer having been largely ignored. The tracer has been left to work in his own shadow, or with images of reduced effective intensity, or has undergone undue strain from uncomfortable position while tracing or from stray light striking the surface upon which the tracing was being made. All of this has been to the detriment of accuracy and convenience in Working with the apparatus. The present invention overcomes the stated difficulties With very simple equipment.

Referring now more particularly to Fig. 1, there is shown at numeral I an elongate, horizontal, rectangular, box-like structure mounted upon a suitable base 3, the latter being supported, for example, upon legs 5. The bottom, sides and ends of the structure I are substantially light-tight. Its top surface 'I is made up of two pieces of transparent glass 9 and II. Other transparent materials may be used at these locations.

The surface 'I composed of the glass sheets 9 and II is located at a convenient elevation for providing a working surface for a draftsman working around the sides of the device. Thus the surface I is not unlike that of a horizontal draw-V ing table or desk. It is readily seen, however, that if it should be desired to perform all the operations from one side of this box, then the box and all the mechanism therein could be arranged to allow the mechanism and top to be tilted at a convenient angle toward that one side.

A light-tight partition I3 divides the box I into unequal coaxial compartments I5 and I'i. This partition I3 extends upward above the surface 1, as indicated at I9, to prevent stray light as from the source used to illuminate the projected data and which may impinge upon one of the pieces of glass 9 or I I from reaching the other. Light is obtained locally from an adjustable light source such as shown at 2 I, which may be directed either toward the glass Il or the glass 9. This light source may be of the fluorescent variety which at high intensity operates at a relatively low temperature.

Joined around an opening 23 thro-ugh the partition I 3 is a camera-type of extensible bellows 25. This joins with the barrel element 21 of a photographic projection lens 29. The bellows 25 prevents light from passing through the partition I3, except through the lens 29. On the other side of the partition I3 is a hood or shade 3| which securely fastens the extensible bellows to the partition and which is adapted to minimize passage of stray light from the compartment I5 to the In the short compartment I 'I is a reflecting mirror 33 shown located at an' angle of approximately to the axis of the lens and also to the plane pf glass II. This mirror vis fixed in position and is adapted to project light rays from the upper surface f the glass II through the lens 29, as indicated by the rays as shown at 35. The direction of the light path of course may be reversed.

The barrel element 21 of the lens is supported upon a lens carriage 3T, having lugs 39 through Which are threaded rotary control rods 4I (Fig. 3) The latter have individual end bearings 43 at the bottom of the partition I3. At their other ends the rods 4I carry attached pinions 45. The pinions are connected by a gear train 41. Since there are three gears in this train, and all function as idlers, the angular motions of the control rods 4I are equal. One of the rods passes through an end wall of the box I, where it is provided with a control wheel 49. By cranking the wheel 49, the axial position of the lens 29 may be adjusted with respect to the mirror 33. In the model illustrated the lens mount is beveled on its lower side, as indicated at 5I, to allow as close an approach as possible to the surface of the mirror 33.

In. the long compartment I5 is an axially movable mirror 53, also located substantially at a 45 angle with respect to the axis of 'the lens 29 and to the glass 9, and adapted to receive light rays from the lens 29 and project them upwardly toward the upper surface of the glass 9. The direction of this light path also may be reversed. This mirror 53 is mounted upon a movable carriage 55, the latter including threaded gears 5l for threaded engagement with threaded control rods 59, located at the bottom of compartment I5. The inner ends of these rods are in separate bearings 6I. It is to be understood that the bearings 6l are separate from the bearings #3, so that the rods 59 may be Voperated independently of the rods 4 I.

As shown in Fig. 6, the rods 59 carry attached pinions 63 connected by an idler gear train 65, which causes the two rods to have the same angular velocity when one of them is rotated. One of the rods passes through an end Wall of the box I, and is provided witha control wheel 61. When the control wheel 61 is turned, the position of the mirror 53 is adjusted axially in the compartment I5. At the lower end of the mirror is a pointer 69 which traverses a scale 'II drawn on the bottom of the box I and'visible' through the glass 9. This scale 'II is" computed to indicate the degree of enlargement or reduction obtained when the mirror Y53 is located at any arbitrary position along the scale. It could be placed in many other conveniently accessible positions as, for example, along one side of the top of the box and the scale read by a pointer attached to the top of the mirror 53l In combination with this scale 'II for facilitating the setting of the position of the movable mirror 53 for a predeterminded degree of enlargement or reduction, a corresponding scale 91 also computed for the particular lens used in the projector may be mounted in 'some convenient position in compartment IT, as shown. A pointer 99 is moutned upon the lens carriage and traverses this scale 91. This facilitates the processof focusing the projector since both the mirror and lens can be quickly set in their approximate proper positions and' final fine adjustments made as necessary. The scaleA ill/.and pointer 99 may be placed elsewhere.

In order to protect from the light any unneeded parts of the mirror 531, a. black curtainroll is provided at '13. This roll is located ycross-wise at the bottom of the mirror and has a spring'winding bias operative toward' Winding down .the llridn 11. The other end of the curtain is wound upon acylinder 15, which is frictionally held in bearings 'I8 and exteriorly provided with a crank 79. The shaft 'I5 has an extension which passes out of the box I through a slot BI providing for its longituidal movement along with the movement of the mirror 53. As indicated in Fig. 7, the curtain Tl has in it a series of framing openings 89, 8I and 82 of different sizes. Thus by operating the crank 19, one or the other of the openings 85, 8| or S2 may beplaced over the mirror 53. Hence only necessary parts of the mirror are exposed for projection and stray light reflections are reduced.

It will be appreciated that an apertured curtain or any other masking device may be used anywhere in the path of the projection beam to reduce the effective field of the lens to the lesser portion desired or needed for any particular projection. However, the most advantageous positions for the apertured curtain 'I1 or other masking device are those near the reectors 33 and 53 or near the glass Working surfaces 9 and II because the beam then would be intersected in a less intense portion thereof and light more readily absorbed and less readily scattered within the bellows 25 or compartments I5 or 17.

At I-I is shown a horizontal light ray through the center and coincident vwith the axis of the lens 29. I'he respective distances measured from the points B and D where this ray strikes the mirrors 33 and 53 respectively, up to the top working surfaces of the coplanar glass sheets 9 and I I are preferably approximatelyequal to the focal length of the lens29.. Thus each of the distances B-C and D-E approximate the focal length. This condition provides for approximately a maxinum range of ratios of enlargement 0r reduction for a given length of the box I consistent with the maximum utilization of the corrected eld of the lens 29, particularly at loW ratios of enlargement or reduction. Such an arrangement, then, permits the maximum iield to be projected at ratios near 1:1 and still permits the lens 29 to make the distance A-B-C a minimum consistent with the clearance needed between the lens and the mirror necessary for high projection ratios of, for example, 1:4 (or 4:1) or even 1:6 (or 6:1) with the form of the invention shown.

In Fig, 8 is shown a form of the invention for higher ratios of enlargementand reduction, in which like numerals designate like parts. In this case it is desirable to use as short a focal length of lens as possible. Thus to make the distance A-B-C as small as possible, the glass II is lowered in position with respect to the lens as indicated at the step portion 85. In this case C- i3V is preferably less than the focal length of the lens but E'-D is greater. Otherwise this form of the device is similar to'thatalready described.

In the case of Fig. 1, the ratio of enlargement is equal to the distance vIn the case of Figure 8 it is Thus in the case of Fig. 8,- the length AAB; is considerably reduced by the step 35.

The box I, besides producing the forni of a convenient working desk, also acts as an enclosure for lthe optical parts and protects them vagancia r'against undue collection of dust and the like.

Operation. `is as follows:

Assume that an enlargement is desired from 'transparent data, such Vas a transparent -map M 'laid over the glass Il. .2| shining through this .map in effect forms an object .for the .projection lens 29. This is refiected from the mirror 133 and projected through the .lens 29. The movable mirror 53 is set with its pointer 69 on the scale TH, showing the degree -of enlargement desired. rIhis .is done by crankting the hand 'wheel 67.. Then the hand Wheel 49 is cranked .to adjust the .lens 29 .until focus is obtained. The result will bean image on any piece of transparent .tracing paper or the like that .may lie upon the glass .9. This vthen may be traced conveniently. The image is indexed I in Fig. 1 and is upright longitudinally with respect to the map M. Light from the light source 2i shining upon the map M is prevented from reaching the glass 9 by the .partition I9, so that it does not interfere with the clarity of image I. Any undesired or unused .portions of the field of the projecting lens are masked by using an appropriate aperture of the curtain 1l.

If it is desired projectively to reduce the data lfor tracing under the above conditions, the lamp 2| is placed at the dotted-line position shown in Fig. 1, the map M is placed over the glass 9 and the tracing paper over the glass I i.

It will be understood that, although the primary purpose of the apparatus is for manual tracing, the image I could be registered photo- 'graphically on any sensitized material lying on the projection surface and subjected to the projection light while being suitably rprotected from vsurrounding light.

Although the control wheels vEi'i and 49 are 4shown as being independently manually adjustable, the screws 4l and 59 or other motiv-e means such as rack and pinion gears could be connected through an auto-focus linkage for simultaneously adjusting the positions of the lens 29 and 'the mirror 53. Thus change of projection ratio could .be accomplished without loss of focus. 'Such other motive .means vand auto-focus devices are old and therefore not shown.

In Figs. 9 and 1'0 is shown another form of the invention in which an `inside light source is used. Like numerals designate like parts. In this case, the device has been shown as set up for a 1:1 projection, instead of 2.5: 1, as in Fig. l.

Two light sources are used: The rst, located 4in compartment il beneath the mirror 3d is a flight source consisting of `a horizontal bank 81 of fluorescent tubes 89. The 'second is a similar :bank 9i of iluorescenttubes 93 supported upon the carriage 55 beneath the mirror 54 in `compartment I5. For the light from either of these sources to illuminate an object on the transparent top 1 for projection, both mirrors 34 and 54 must be of the partially silvered type such as are used in interferometers. These mirrors are silvered only to such a degree that part of the light from behind them, such as from the lights 89 or 93 respectively, will be reflected while the remainder will pass through and beyond the mirror to illuminate an object upon the transparent working surface ll or 9.

In Fig. 9 this partial reflection and partial transmission of light is illustrated respectively .by the arrows 3-6 and 3B which represent rays of light from the lamps j3S). light which is reiiected as shown by arrow 3S is absorbed by means of suitable, preferably dead The 'light from the lamp The portion of the black surfacing within .the compartment -l'l `be hind the mirror 34 .sonnone `of it will be reflected back through the mirror to interfere with the image being projected. The light which .passes through the 'mirror as shown by arrow 38 is yreflected from the object on the transparent t-op Il, .then behaves exactly as light transmitted .through a transparent object which would be illuminated from above as by the lamp 2| of Fig. 1; i. e., this `light from the 'object Vwould be reflected in part from the mirror 34 to and through the lens 29 then 'reflected in part again from the mirror y54 and brought to a focus at the tra-ns- Yparent working lsurface 9. 'Of course some of the light would be lost in the several reflections from partially silvered surfaces, 'but the advantage gained in permitting the projection of images from surfaces which may be opaque or which may have markingsfon the reverse side would in many instances warrant the inclusion Iof this special feature despite -its several complications regarding construction and the extra expense of the special mirrors.

The advantages of both the model for projecting from transparent data and the model for projecting from opaque data -could be had with a single Vinstrument having the lights mounted below the mirror mounts las shown in Figs. 9 and 10. A set of three mirrors one of which is partially yreflecting to be used with one of the other Ytwo mir-rors which are totally reflective wou-ld be carried on hand. The mirrors may be fitted interchangeably, using either two totally reflective ones or one partially reflective one anda totally reflective one in either compartment l5 or i-'I respectively.

The lights 89 and y93 are placed in a position low enough with respect to the mirrors 54 `and `3'4 so that no light which passes directly from either of these sources strikes the lens 29.

Provision is made for switching on and off either light bank 8l or 9i. Thus, when the data is placed over the glass il for projection to the glass 9, only the lights 89 are lighted; whereas, when the data is placed Aon the .glass 5 and projected to the glass Il, the lights 89 are turned out and lights 93 are turned on. This form of the invention permits the operator to project the markings from one side of `a, sheet without inter- `ference from markings on the other side, suchas for example a page of a book.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

vAs many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all lmatter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. `A projector comprising a horizontally 'elongate box, van upper transparent wall vfor said box providing lconvenient working ysurfaces for tracing projections thereon, an essentially light-tight dividing Vpartition within said box, said partition having an opening, essentially light-tight ex- 'tensible means attached around said .opening and extending into one compartment, 'a lens carriage, va .lens on the carriage, said eXtensible means .being attached to said carriage, va xed reflector in 'said one compartment located at substantially 45 with respect to the axis of said lens and-to .the upper surface of the box, means for adjusting 'the position of said carriage with respect to said reflector, a movable reflector in the other compartment also located substantially at 45 with respect to the axis of said lens and to the upper surface of the box, and means for adjusting the position of said last-named reflector along the axis of said lens.

2. A projector comprising a horizontally elongate box, an upper lateral and transparent wall for said box providing convenient lateral Working surfaces for tracing projections thereon, a vertical partition within said box dividing it into a relatively short -compartment and a relatively long compartment, said partition having an opening, extensible means attached around said opening and extending into the short compartment, a lens carriage, a lens en the carriage, said extensi-ble means being attached to said carriage, a fixed reflector in said short compartment located substantially at 45 with respect to the axis of said lens and the upper surface of the box, means for adjusting from the exterior of the box the position of said carriage and lens with respect to said reiiector, a movable reflector in the long compartment also located substantially at 45 with respect to the axis of said lens and to the upper surface of the box, and means for adjusting the position of said last-named reflector from the exterior of the box.

3. A projector comprising a horizontal elongate box, an upper transparent wall for said box providing a convenient horizontal working surface for tracing projections thereon, a fixed partition within said box dividing it into a relatively short compartment and a relatively long compartment, said partition having an opening, a bellows attached around said opening and extending into the short compartment, a lens carriage, said bellows being attached to said carriage, a lens on the carriage, a fixed reflector in said short compartment located at an angle of substantially 45 with respect to the axis of said lens and the upper surface of the box, means for adjusting from the exterior of the box the position of said carriage with respect to said reiiector, a movable reector in the long compartment also ylocated at an angle of substantially 45 with respect to the axis of said lens and the upper surface of the box, and means for adjusting the position of said last-named reflector from the exterior of the box along the axis of said lens, an adjustable masking device for limiting the cross section of a beam passing to and from the working surface and through the lens.

4. A projector comprising an elongate substantially horizontal box, an upper transparent substantially horizontal wall in said box, said wall forming a convenient Working surface for tracing projections on the upper wall, a partition in the box having an opening therethrough, extensb-le means attached to the partition around said opening, a lens carriage in one of the compartments having said extensible means attached thereto, a lens on the carriage, means for axially adjusting said lens carriage from a point outside of the box, the axis of said lens being located below said transparent working surface at approximately the focal length of the lens, a xed reflector located in the compartment containing the lens and located at an angle of substantially 45 with respect to the lens axis and to said upper working surface, an axially movable reiiector in the other compartment movable along the axis of said lens and located at an angle of substantially 45 with respect to said axis and to said -upper working surface, and means for adjusting the axial position of said last-named reflector operable from the exterior of the box.

5. A projector comprising a projection box having a transparent wall providing a working surface for tracing projections thereon, a fixed light-tight partition dividing said box into two compartments, said partition having an opening, essentially light-tight extensible means extending around said opening and extending into one compartment, a lens carriage in said one compartment, a lens on the carriage, said extensible means being connected around the lens, a fixed reector in said one compartment located at substantially 45 with respect to the axis of said lens and to said transparent wall of the box, means for adjusting the position of said carriage with respect to said reflector, a movable reflector in the other compartment also located at sub'- stantially 45 with respect to the axis of said lens and to said transparent wall, index means associated with said movable reflector to indicate degrees of enlargement on reduction, and means for adjusting the position of said movable reflector in the direction of the axis of the lens.

6. A projector comprising an elongate horizontal box, a transparent wall forming the top side of said box and providing a working surface for tracing projections thereon, a xed lighttight partition dividing said box into a short and a lonsT compartment, said partition having an opening, essentially light-tight extensible means extending around said opening and extending into the short compartment, a lens carriage in said short compartment, a lens on the carriage, said extensible means being connected around the lens, a fixed reector in said short compartment located at substantially 45 with respect to the axis of said lens and to said transparent wall, means for adjusting the position of said carriag-e with respect to said reiiector, a movable reiiector in the long compartment also located at substantially 45 with respect to the axis of said lens and to said transparent wall, index means associated with said movable reflector to indicate degrees of enlargement, and means for adjusting the position of said movable reector in the direction of the axis of the lens.

7. A projector comprising an elongate box, an elongate transparent Wall forming one side of the box and pr-oviding a working surface for tracing projections thereon, a partition within the box, a light-resistant member extending from the working surface near the plane of said partition, said partition having an opening, essentially light-tight extensible means attached around said opening and extending into one compartment, a lens carriage, a lens on the carriage, said extensible means being attached around the lens, a reflector in said one compartment, means for adjusting the position of said carriage with respect to the reflector, a reflector in the other compartment, and means for adjusting the position of the last-named reflector.

8. A projector comprising a projection box having a transparent wall providing a work-ing surface for tracing projections thereon, a iixed light-tight partition dividing said box into two compartments, said partition having an opening, essentially light-tight extensible means extending around said opening and extending int-o one compartment, a lens carriage in said one ccmpartment, a lens on the carriage, said extensible means being Yconnected around the lens, a nxed reflector in said one compartment located at substantially 45 with respect to the axis of said lens and to said transparent Wall of the box, means for adjust-ing the position of said carriage with respect to said refiector,a movable reflector in the other compartment also located at substantially 45 With respect to the axis of said lens and to said transparent Wall, index means associated with said movable reector to indicate degrees of enlargement or reduction, index means associated With the lens to indicate conditions of focus of the lens for the respective enlargements or reductions, and means for adjusting the position of said movable reflector in the direction of the axis of the lens.

9. A projector comprising an elongate box, said box having a transparent Working surface on one side, a partition Within the box forming tWo compartments therein, an adjustable lens associated with the partition, the axis of which lens is substantially parallel to said Working surface, a mirror in each compartment located substantially at 45 with respect to the axis of the lens for projection between the parts of said Working surface associated with the respective compartments, one of said mirrors being adjustable along 10 the axis of the lens, index means associated with said adjustable mirror for indicating degrees of enlargement or reduction, and index means associated with said lens for indicating conditions of focus of the lens for the respective enlargements or reductions.

THOMAS C, FURNAS, JR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

